1. Field
The present teachings relate to radio-frequency (RF) amplifiers used in RF circuits. More particularly, the present teachings relate to methods and systems for RF amplifiers with variable feedback impedance capable of high output power and high output voltage swings while maintaining high output linearity and high output linear range.
2. Description of Related Art
RF amplifiers are an important part of present days RF communication systems as they constitute the main system block that drives the antenna in any radio transmitter. As such, linearity and power efficiency (e.g. gain) of such amplifiers are sought after attributes for integrators of such devices. Unfortunately these two sought after attributes work against each other as amplifier output tends to become non-linear when operated at higher gains required for better power efficiency. Feedback (e.g. using a combination of resistors, capacitors and inductors) is one of the methods universally known in the art used to trade off amplifier gain for linearity.
As used in the present disclosure, the term “IC” can refer to an integrated circuit or monolithic integrated circuit composed of a set of electronic circuits on one small plate (“chip”) of semiconductor material such as silicon. An IC can also be referred to as a “chip” or a “microchip”. The set of electronic circuits within an IC are typically made of a very large number of transistors and other electronic components, which may need supply power (e.g. positive supply and negative supply) to operate.